Formation of cationic molybdenum η²-vinyl complexes; structural evidence for the coupling of η²-vinyl and alkyne ligands

Abstract

Protonation (HBF4·Et2O) of [MoX(η2-MeC2Me)2L](X = Cl, Br, I; L =η-C5H5 or η5-C9H7) affords the cations [X[graphic omitted]HMe(η2-MeC2Me)L][BF4], which react with LiX to give [X2[graphic omitted]HMe(η2-MeC2Me)L] or with PR3(R = Me, or OMe) to give the C–C coupled products [XMoC(Me)-η3-{C(Me)C(Me)CHMe}(PR3)(L)][BF4], the latter being structurally identified by X-ray crystallography; carbon–carbon coupling also occurs on reduction of [Br2[graphic omitted]HMe(η2-MeC2Me)(η-C5H5)] with Mg/Hg in the presence of CO to form [MoBr(CO){η4-CHMeC(Me)·C(Me)CHMe}(η-C5H5)], and treatment of the phosphine promoted coupled products with Li[N(SiMe3)2] leads to reversible deprotonation reactions affording [MoX{η4-CHMeC(Me)·C(Me)CCH2}(PR3)L].